You probably will not get all the heat you need if the skid was originally 5 or 5.5gpm since the coil is a certain size, Call Russ J. at Southside equipment. I was going to do the same thing with a skid I have but was told by several people that the water might not get hotter than 140 degrees when you go from 5.5gpm to 8gpm and have the same coil and burner.
If they changed out the pump, engine, coil and burner, that would be very expensive to do the job right, chances are they might have only changed out the pump and maybe the engine. If you think about it, the coil can easily be over $1000, the pump is probably about $700, the larger engine would probably be about $1500 to $2000, and the burner assembly installed is probably over $600. When you look at it this way, I don't see many people doing all of that for that price when you can just sell that rig and buy an 8 gpm skid ready to use or buy a used 8gpm skid.
The skid that is made 8gpm from the factory is what I would do if that is what you want/need.
You can get the info from the guy about the company that did the modifications and call them to see what they did, it would suck if you bought the rig and it will not get hot enough to remove years old gum and not be able to clean dirty/greasy commercial concrete areas where you need hotter water than 140 degrees.
A few phone calls might save you a lot of money and a lot of aggravation. Just my opinion.
